In the field of magnetic heads to be mounted on a magnetic recording apparatus such as a hard disk drive (HDD), recently, the recording method is being shifted from longitudinal recording to perpendicular recording in order to improve the recording density with respect to a magnetic recording medium such as a hard disk. The perpendicular recording method achieves high linear recording density and also has an advantage that the recording medium after recording becomes highly resistant to heat fluctuation.
A perpendicular recording magnetic head is provided with a coil film for generating a magnetic flux and a magnetic pole film for guiding the magnetic flux to a recording medium. In a HDD using this perpendicular magnetic head, the recording medium can be magnetized by a perpendicular magnetic field for recording.
In the production process of the perpendicular magnetic head, the end width (or trailing edge width) of the magnetic pole film, which defines a recording track width, has to be decreased as much as possible in order to meet an increase in surface recording density. As means for decreasing the trailing edge width, for example, Japanese Unexamined Patent Application Publication No. 2001-323393 discloses a method of forming a resist pattern to have an opening, then narrowing the opening by forming an insoluble film to cover the resist pattern, and then forming a plated film in the opening formed with the insoluble film.
Japanese Unexamined Patent Application Publication No. 2003-017474 also discloses a thin-film patterning method of forming a strippable film and a resist pattern with an opening on a thin film in the mentioned order, subsequently narrowing the opening by forming an additional film to cover the resist pattern, and then etching the thin film using the resist pattern and the additional film as a mask.
As a method for forming a magnetic pole film, Japanese Unexamined Patent Application Publication No. 2002-092821 discloses a method of forming a depression in an inorganic insulating film by etching the inorganic insulating film using a resist pattern as a mask, then removing the resist pattern, then forming a stopper film and a magnetic film in the mentioned order to cover the inorganic insulating film, and then polishing the magnetic film until the stopper film is exposed. In this method, a main magnetic pole film having an inverted trapezoid cross-section can be formed in the depression after polishing.
In manufacturing fields related to today's thin-film devices, moreover, ALD (atomic layer deposition) is adopted as a film formation method which is extremely excellent in controlling the film thickness (for example, “ALD atomic layer deposition apparatus” by Techscience Ltd., Internet <URL: http://techsc.co.jp/products/mems/ALD.htm>). This ALD is a method capable of forming an ultrathin, dense oxide, nitride or metal film under a high temperature equal to or greater than 150 degrees centigrade and adopted in manufacturing fields where physical properties such as withstand voltage are strictly demanded.
In the magnetic head manufacturing field, ALD is used in the formation process of a reproducing gap of a reproducing head (for example, the specification of U.S. Pat. No. 6,759,081).
In order to improve the recording capacity of a hard disk drive (HDD), meanwhile, the recording resolution must be improved by increasing the coercive force of the medium while increasing the track density by reducing the magnetic pole film width of the magnetic head. In order to assure sufficient overwrite characteristics with respect to a medium of a high coercive force, a high saturation magnetic flux density material such as an FeCo-type material, a CoNiFe ternary alloy film, FeC or FeN has to be used for the magnetic pole film.
Also in perpendicular magnetic heads, the recording capacity can be improved by using such a high saturation magnetic flux density material for the magnetic pole film.
However, the perpendicular magnetic heads have a problem that a signal recorded by the magnetic pole film on the magnetic recording medium becomes erased when recording is not performed, and this problem is called “pole erase”.
In the perpendicular magnetic heads, a soft magnetic film for recording has its hard axis directed along an ABS direction to perform recording in magnetization rotation mode. That is, residual magnetization along the ABS direction is minimized to prevent an excess magnetic flux from being generated when recording is not performed, thereby avoiding the pole erase. In order to assure this function, the coercive force of the magnetic pole film has to be kept low.
However, if there is taken a manufacturing method in which the magnetic pole film is formed by a plated film, the crystal grain size in the plated film growing on a seed film (or electrode film) tends to increase with distance from the seed film as the film growth progresses. The coercive force Hc increases with increase in the crystal grain size. Therefore, the demand for low coercive force on the magnetic pole film cannot be met.
Particularly in the perpendicular magnetic heads, since the write magnetic pole has its write end at the trailing edge remote from the seed film, there is a particular problem that the crystal grain size increases at the very end important for writing, which leads to increase in the coercive force, and therefore, it is greatly desired to solve the problem of increase in the coercive force due to increase in the crystal grain size.